Ui Button using voforia,Ui Button AR using Vuforia

Hi. I am making thesis about AR Maybe this is really simple question but i can't Figure out. :(

I have a Ui Button in my scene I want when I press the button and show AR model.

i am using vuforia ground plane

something like this https://www.youtube.com/watch?v=ZDWRl9A1p6s

Please help me. Sorry for my bad English